This U. S. Geological Survey professional paper discusses aspects of the geology of titanium as a framework for appraising resources of this commodity in the light of today's technology, economics, and geologic knowledge. Contents: Titanium Contents and Titanium Partitioning in Rocks by E. R. Force Metamorphic Source Rocks of Titanium Placer Deposits - A Geochemical Cycle by E. R. Force Rutile and Sphene in Blueschist and Related High-Pressure-Facies Rocks by M. C. Blake, Jr. and Benjamin A. Morgan Titanium Deposits in Anorthosite Massifs by Norman Herz Titanium Deposits in Alkalic Igneous...